This invention relates to a device for treatment of tear-related disorders. More specifically, this invention relates an improved punctum plug for treating keratoconjunctivitis sicca and other conditions of dry eye and contact lens wearing problems as well as pathologically dilated and constricted puncta. Keratitis sicca or keratoconjunctivitis sicca or in laymen's terms "dry eye" pertain to a continuum of difficulties which range from discomfort to decreased vision and pain and in extreme circumstances blindness. The causes of dry eye are aging, disease inflammatory processes and prescription drug side effects. A common condition is an inability to maintain a stable preocular tear film (PTF).
In a healthy eye the PTF is spread over the cornea and conjunctival epithelia by the upper eyelid and makes the surface of an eye smooth and optically clear. The tear film is composed of three thin layers which coat the surface of the eye. An outermost oily layer is produced by small glands called meibomian glands which are located at the edge of the eyelid. This outermost layer provides a smooth tear surface and reduces evaporation of tears. A middle watery layer is produced by large lacrimal glands and a plurality of small glands scattered throughout the conjunctiva. This watery layer produces the largest amount of fluid and cleanses the eye by washing away foreign particles and irritants. An innermost layer consists of mucus produced by goblet cells in the conjunctiva. This inner layer allows the watery layer to spread evenly over the surface of the eye and helps the eye to remain wet. The mucus produced by this innermost layer adheres tears to the eye.
Normally the PTF is formed by a cooperative interaction of products from the memobian glands, the lacrimal glands and goblet cells. Dry eye results when those glands produce less than an adequate amount of tears or the tears are drained away or evaporate too rapidly.
Tear deficiencies cause chronic irritation of the anterior segment, resulting in complaints of sandy, itching eyes, conjunctivitis, metabolic disturbances of the cornea and extreme cases, a loss of visual function. Patients often present complaints and problems associated with a partial decrease in aqueous tear production. One cause of such complaints is partial atrophy of the lacrimal glands which is seen often in an aged patient and in some patients following infection. Atrophy can also occur in a younger patient wearing high water-contact lenses, because of the increased requirement of the anterior segment of aqueous tears.
Conditions of dry eye have been treated with various degrees of success in the past. One prior practice in treating dry eye has been to utilize various types of topical drops and ointments. Some sufferers of dry eye prefer using humidifiers and vaporizers to increase the moisture level in the surrounding air, which helps by decreasing evaporation of lacrimal fluid from the eye.
More recently, permanent punctal occlusion has proven to be an effective method of treating tear-related disorders including dry eye, corneal ulcers, conjunctivitis, blepharitis, contact lens problems and other external eye diseases. In extreme cases of discomfort and pain, such as occur in Sjogren's syndrome, permanent closure of the puncta and canaliculi by surgery or cauterization has produced at least some success. Thermal occlusion was initially performed with cautery or diatherapy, and is now more frequently performed with the aid of medical grade lasers. When PTF loss into the naso-lacrimal trap is blocked, the volume of the remaining tears provide enhanced wetness of the anterior segment.
Each of the aforementioned treatments, however, possess certain inherent limitations. Topical drops and ointments require frequent re-applications. Humidifiers and vaporizers are relatively bulky and must be connected to an electrical source and, thus, are not satisfactory for all occasions, such as outdoor activities. Finally, surgical or cauterization procedures are costly and create a danger of subsequent epiphora and/or infection, the destruction of normal tissue requires surgical intervention to reverse.
In order to avoid one or more of the foregoing disadvantages, alternative methods of temporary or reversible occlusion of a punctal opening have been envisioned. Such methods include temporary occlusion of the canaliculus by the insertion of small rods made from gelatin or collagen, or the use of temporary plugs made from bone cement. The blocking action of these agents is either to brief or otherwise unsatisfactory.
The foregoing noted problems of mild to moderate dry eye were advantageously addressed by the introduction of a punctum plug which advantageously provides reversible punctal occlusion as disclosed and claimed in the previously identified Freeman U.S. Pat. No. 3,949,750. The disclosure of this patent, of common inventorship with the subject invention, is incorporated here in by reference as though set forth at length.
Occlusion of a lower and/or upper punctum with medical grade silicone plugs of the Freeman design has proven to be highly beneficial in a number of patients suffering from dry eye conditions.
It has been found however, that in certain instances a punctum plug of previously known designs have been subject to occasional extrusion or accidental removal by a patient rubbing the corner of an eye. Accordingly, it would be highly desirable to facilitate the retention and function integrity of a punctum plug within the punctum of a patient's eye while providing the advantages of reversibly blocking the flow of lacrimal fluid from the eye.
The problem suggested in the proceeding are not intended to be exhaustive, but rather are among many which may tend to reduce the effectiveness of prior methods and apparatus for blocking the flow of lacrimal fluid through a punctum and associated canaliculus. Other noteworthy problems may also exist; however, those presented above should be sufficient to demonstrate that devices for treating the loss of PTF appearing in the past will admit to worthwhile improvement.